The present invention generally relates to railway draft vehicles used to move railcars along railroad track, also referred to as rail movers or rail car movers. More specifically, the present invention relates to such a draft vehicle that has an improved steering and propulsion control over front and rear wheel assemblies.
Rail draft vehicles are typically found in rail yards or industrial sites for moving single or groups of rail cars to form trains. These vehicles feature rubber tired wheels for contacting the rails, since it has been found that such wheels have a higher coefficient of friction with the rails than steel wheels and are thus able to develop increased pulling power compared to steel wheeled vehicles. Since railroad track conforms to the underlying terrain, track typically includes inclines, banked turns and hills, all of which need to be accommodated by rail draft vehicles. Steering of such vehicles is achieved using independently pivoting front and rear wheel assemblies. To effect a turn, the front wheels pivot in one direction, and the rear wheels pivot in the opposite direction. However, it can be difficult to maintain the road wheels on the rails. Thus, there exists a need for a rail draft vehicle that relatively consistently maintains the road wheels on the rails.
Another drawback of conventional rail draft vehicles is that the wheels are configured for being steered in the same manner as a conventional truck. This means that any universal joints are located at a conventional location at the ends of the front or rear axle next to each of the road wheels. Thus, a need exists for a rail mover with a relatively simpler power transmission system.
Conventional units of this type employ separate hydrostatic motors for independently driving the front and rear axles. Representative units are described in U.S. Pat. No. 3,434,432. These units are relatively expensive to build and maintain.
Another drawback of conventional rail draft vehicles is that there are heavy loads on the front and rear axles, which are independently powered as described above. Accordingly, the respective joints, bearings, and other drive system components experience significant wear, and in some cases, failure. Increased wear is particularly present when the vehicle negotiates a turn, because the connection between the wheel axle and the transmission is offset. To address this, conventional draft vehicles use U-joint connections in the drive trains. However, this type of connection results in fluctuations in rotational velocity. Drawbacks of these systems include accelerated wear on the vehicle components. As such, there is a need for an improved drive system for rail car movers.